The present invention generally relates to recliner assemblies for seats and more particular to an improved linear recliner assembly for reducing undesirable movement when the assembly is locked.
Occupant safety and comfort are paramount concerns for automobile manufacturers. In particular, vehicle seating systems are a significant focus for improved comfort and safety even as manufacturers add more functions and improve versatility of seat assemblies. For example, conventional vehicle seating systems include reclining seats that enable comfort adjustment by a vehicle occupant. As more functions and features are added, manufacturing a reliable, safe, and cost-effective seat assembly becomes an increasing challenge.
In many reclining seats, a linear recliner mechanism includes a recliner rod that reciprocates relative a recliner mechanism housing. The reciprocating recliner rod is pivotally connected at one end to a long lever arm, usually the seatback, against which various forces are applied. The linear recliner mechanism in a vehicle seat is quite small when compared with the length of a seatback, and vehicle vibration or movement of an occupant may impose various forces upon that lever arm during use. Because these forces are applied along such a lengthy lever arm, a large moment is imposed about the recliner rod""s pivotal connection to the lever arm, whereby the effects of any variations in the components of the recliner mechanism are magnified. Such play or backlash between the engaging teeth or clearances in the mechanism components allow the seatback to move a miniscule amount even when the mechanism is locked. These small excursions are magnified by the length of the lever arm and become noticeable at the upper end of the seatback. For example, the seatback of an unoccupied seat may tend to oscillate When the vehicle encounters rough road conditions. This magnified play in a recliner mechanism has been termed xe2x80x9cchuckingxe2x80x9d and refers to any manufacturing variation or play in the mechanism components that allows movement of the lever arm or seatback while the mechanism is in a locked condition.
Additionally, as seat assemblies have been improved by automobile manufacturers, increased seatback loading has resulted from seatbelt systems attached to a top portion of the seatback. In the event of an accident, the forward inertia of an occupant""s body pulls the seatbelt with an extremely large force. Such a large force on the seatback, acting as a lever arm, results in a significant strain within. the recliner mechanism. As a result, recliner mechanisms used with such xe2x80x9call belts-to-seatxe2x80x9d applications (i.e., stand-alone structural seats.) must be sufficiently strong to protect and restrain an occupant during a crash.
Further, as seat assemblies have evolved to include more functions and a greater range of motion, packaging has become a concern. When including a linear recliner mechanism in a seat assembly, a recliner rod that reciprocates relative to the recliner mechanism housing is preferred over a threaded rod that rotates a nut relative the recliner mechanism housing because of these packaging concerns. Also, in such linear recliner mechanisms, an expansion spring is usually mounted coaxially with the recliner rod to bias the seatback to its upright position. Expansion springs generally increase the recliner rod length and limit the packaging options. Further, increased recliner rod length reduces the compressive strength of the recliner rod based upon the principle of column loading.
Therefore, it is desirable in the industry to provide a recliner mechanism that significantly reduces or eliminates chucking of a seat assembly. It is further desirable that such a recliner mechanism be sufficiently strong, providing adequate occupant protection in the event of an accident.
Generally, the present invention provides an improved linear adjustment mechanism for implementation with a recliner mechanism of a seat assembly. The linear adjustment mechanism directs the forces within the locking mechanism to reduce the overall clearances within the recliner mechanism. One advantage of the present invention is the reduced clearances translate into reduced chucking of the seatback relative to the seat. As a result, overall occupant comfort and safety is increased. Another advantage of the present invention is the improved crash performance of the seat assembly. The linear recliner mechanism""s directed forces result in increased strength of the locking members, such that the seatback maintains its position relative to a seat in the event of an accident. This is especially desirable with seatback-mounted seatbelt systems.
To achieve the above described advantages, the present invention provides a linear adjustment mechanism including a bar rack slidably supported in a housing having inner and outer plates. A pawl is pivotably supported between the inner and outer plates for selectively locking the bar rack in one of a plurality of positions relative to the pawl. The pawl is disposed substantially parallel to the bar rack such that in a locked position a linear force applied to the bar rack produces a resultant linear force to the pawl, wherein clearances between the pawl and a pivot of the pawl are reduced.
In a preferred embodiment of the present invention, the linear adjustment mechanism is included in a seat assembly having inner and outer supports and an arm supporting a seatback and rotatably mounted between the inner and outer supports. The arm pivotally interfaces the bar rack such that the arm, and thus the seatback, can be positioned in a plurality of rotatable positions relative to the inner and outer supports, as well as the seat bottom, corresponding to the plurality of positions of the bar rack. Preferably, a return spring biases the arm, and thus the seatback, in a first position corresponding to a dump position of the seatback. Further, the return spring minimizes the length of the bar rack, thus maximizing its column loading strength.
Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.